Flask



FIG. 1 is a top plan view of a flask showing my new design;

FIG. 2 is a front elevation view thereof, the rear elevation view being identical; and,

FIG. 3 is a bottom plan view thereof.

The broken line illustration in FIG. 3 shows environmental structure and is not part of the design sought to be patented. 

The ornamental design for a flask, as shown and described. 